Cu-doped TiO(2) nanoparticles enhance survival of Shewanella oneidensis MR-1 under ultraviolet light (UV) exposure

Combination of magnetic field and ultraviolet for fouling control in saline wastewater distribution systems

Fouling is a significant challenge for recycling and reusing saline wastewaters for industrial, agricultural or municipal applications. In this study, we propose a novel approach of magnetic field (MaF) and ultraviolet (UV) combined application for fouling mitigation. Results showed, combination of MaF and UV (MaF-UV) significantly decreased the content of biofouling and reduced the complexity of microbial networks, compared to UV and MaF alone treatments. This was due to MaF as pretreatment effectively reduced the water turbidity, improve the influent water quality of UV disinfection and increases UV transmittance, eliminating the adverse impacts of UV scattering and shielding, hence increased the inactivation effectiveness of UV disinfection process. MaF assisted UV also reduced the abundance of UV-resistant bacteria and inhibited the risk of bacterial photoreactivation and dark repair. Meanwhile, MaF-UV drastically reduced the contents of precipitates and particulate fouling by accelerating the transformation rate of CaCO3 crystal from compact calcite to loosen hydrated amorphous CaCO3, and enhancing the flocculation process. These findings demonstrated that MaF-UV is an effective anti-fouling strategy, and provide insights for sustainable application of saline wastewaters.

Sterilization mechanism and nanotoxicity of visible light-driven defective carbon nitride and UV-excited TiO2

The sterilization effect of photocatalysis and biotoxicity of nanomaterial catalysts have attracted high attention. In this study, the novel visible-driven defective carbon nitride (VL/DCN) system exhibits non-photoreactivation, non-toxic superior performance compared with traditional ultraviolet radiation (UV) and UV/titanium dioxide (UV/TiO2). The inactivation of antibiotic-resistant bacteria (ARB) by novel VL/DCN still reached 7 log within 4 h, and the reduction rates of aminoglycoside gene strB and tetracycline gene tetA exceeded 0.8 log and 1.2 log, respectively. Further, the sterilization mechanism and nanotoxicity were contrastively and systematically analyzed among above three systems as following. Firstly, in the VL/DCN system, reactive oxygen species (ROSs) generated from photocatalytic process leads to the destruction of cell membranes, resulting in dissolving out of potassium ion (K+), protein and cell membrane ATP content. Thus, resistant bacteria were completely inactivated and photoreactivation disappears. In contrast, the UV only acted on bacterial DNA and existed the light resurrection. The UV/TiO2 strictly dependent on ultraviolet light and can be used in limited scenarios. Secondly, in cell viability analysis by human lung cell line BEAS-2B experiments, the 10% inhibition of cell growth when DCN was 600 mg/L much lower than 28% inhibition of cell growth when TiO2 was only 200 mg/L. The expression of pro-inflammatory cytokines ((Interleukin, IL) -6), IL-8, IL-1β) under the effect of DCN was 1.5-fold, 5.7-fold and 3.7-fold lower than TiO2, respectively. Meanwhile, DCN induced cells to produce less ROSs, malondialdehyde (MDA), and more superoxide dismutase (SOD). Above results demonstrated that DCN has far lower cytotoxicity than TiO2. This study provides theoretical support for the application of photocatalytic sterilization technology and the exploration of the toxicity of nanomaterials.

Effects of Light on Growth and Metabolism of Rhodococcus erythropolis

Rhodococcus erythropolis is resilient to various stressors. However, the response of R. erythropolis towards light has not been evaluated. In this study, R. erythropolis was exposed to different wavelengths of light. Compared to non-illuminated controls, carotenoid levels were significantly increased in white (standard warm white), green (510 nm) and blue light (470 nm) illuminated cultures. Notably, blue light (455, 425 nm) exhibited anti-microbial effects. Interestingly, cellular lipid composition shifted under light stress, increasing odd chain fatty acids (C15:0, C17:1) cultured under white (standard warm white) and green (510 nm) light. When exposed to blue light (470, 455, 425 nm), fatty acid profiles shifted to more saturated fatty acids (C16:1 to C16:0). Time-resolved proteomics analysis revealed several oxidative stress-related proteins to be upregulated under light illumination.

Application of antibacterial nanoparticles in orthodontic materials

During the orthodontic process, increased microbial colonization and dental plaque formation on the orthodontic appliances and auxiliaries are major complications, causing oral infectious diseases, such as dental caries and periodontal diseases. To reduce plaque accumulation, antimicrobial materials are increasingly being investigated and applied to orthodontic appliances and auxiliaries by various methods. Through the development of nanotechnology, nanoparticles (NPs) have been reported to exhibit excellent antibacterial properties and have been applied in orthodontic materials to decrease dental plaque accumulation. In this review, we present the current development, antibacterial mechanisms, biocompatibility, and application of antibacterial NPs in orthodontic materials.

Facet-Dependent Bactericidal Activity of Ag3PO4 Nanostructures against Gram-Positive/Negative Bacteria

Ag₃PO₄ nanostructures (APNs) containing silver (Ag metal; of the noble metal families) have the potential to exhibit enzyme-mimetic activity. A nanostructure shape, including its surface facets, can improve the bioactivity of enzyme mimicry, yet the molecular mechanisms remain unclear. Herein, we report facet-dependent peroxidase and oxidase-like activity of APNs with both antibacterial and biofilm degrading properties through the generation of reactive oxygen species. Cubic APNs had superior antibacterial effects than rhombic dodecahedral shapes when inhibiting Gram-positive and Gram-negative bacterial pathogen proliferation and biofilm degradation. A similar performance was observed for rhombic dodecahedral shapes, being greater than tetrahedral-shaped APNs. The extent of enzyme-mimetic activity is attributed to the facets {100} present in cubic APNs that led the peroxide radicals to inhibit the proliferation of bacteria and degrade biofilm. These facets were compared to rhombic dodecahedral APNs {110} and tetrahedral APNs {111}, respectively, to reveal a facet-dependent enhanced antibacterial activity, providing a plausible mechanism for shape-dependent APNs material enzyme-mimetic effects on bacteria. Thus, our research findings can provide a direction to optimize bactericidal materials using APNs in clinically relevant applications.

A review on anti-bacterials to combat resistance: From ancient era of plants and metals to present and future perspectives of green nano technological combinations

In the primitive era, humans benefited partially from plants and metals to treat microbial infections. Later these infections were cured with antibiotics but further suffered from resistance issues. In searching of an alternative, researchers developed an adjuvant therapy but were hampered by spreading resistance. Subsequently, nanoparticles (NPs) were proposed to cease the multi-drug resistant bacteria but were hindered due to toxicity issues. Recently, a novel adjuvant therapy employed metals and botanicals into innovative nanotechnology as nano-antibiotics. The combination of green synthesized metallic NPs with antibiotics seems to be a viable platform to combat against MDR bacteria by alleviating resistance and toxicity. This review focuses on the primitive to present era dealings with bacterial resistance mechanisms, newer innovations of nanotechnology and their multiple mechanisms to combat resistance. In addition, special focus is paid on greener NPs as antibiotic carriers, and their future prospects of controlled release and toxicity study.

Nano-therapeutics: A revolution in infection control in post antibiotic era

With the arrival of antibiotics 70 years ago, meant a paradigm shift in overcoming infectious diseases. For decades, drugs have been used to treat different infections. However, with time bacteria have become resistant to multiple antibiotics, making some diseases difficult to fight. Nanoparticles (NPs) as antibacterial agents appear to have potential to overcome such problems and to revolutionize the diagnosis and treatment of bacterial infections. Therefore, there is significant interest in the use of NPs to treat variety of infections, particularly caused by multidrug-resistant (MDR) strains. This review begins with illustration of types of NPs followed by the literature of current research addressing mechanisms of NPs antibacterial activity, steps involved in NP mediated drug delivery as well as areas where NPs use has potential to improve the treatment, like NP enabled vaccination. Besides, recently emerged innovative NP platforms have been highlighted and their progress made in each area has been reviewed.

The antimicrobial activity of nanoparticles: present situation and prospects for the future

Nanoparticles (NPs) are increasingly used to target bacteria as an alternative to antibiotics. Nanotechnology may be particularly advantageous in treating bacterial infections. Examples include the utilization of NPs in antibacterial coatings for implantable devices and medicinal materials to prevent infection and promote wound healing, in antibiotic delivery systems to treat disease, in bacterial detection systems to generate microbial diagnostics, and in antibacterial vaccines to control bacterial infections. The antibacterial mechanisms of NPs are poorly understood, but the currently accepted mechanisms include oxidative stress induction, metal ion release, and non-oxidative mechanisms. The multiple simultaneous mechanisms of action against microbes would require multiple simultaneous gene mutations in the same bacterial cell for antibacterial resistance to develop; therefore, it is difficult for bacterial cells to become resistant to NPs. In this review, we discuss the antibacterial mechanisms of NPs against bacteria and the factors that are involved. The limitations of current research are also discussed.

A mechanistic study of TiO2 nanoparticle toxicity on Shewanella oneidensis MR-1 with UV-containing simulated solar irradiation: Bacterial growth, riboflavin secretion, and gene expression

Toxicity of nanomaterials to ecological systems has recently emerged as an important field of research, and thus, many researchers are exploring the mechanisms of how nanoparticles impact organisms. Herein, we probe the mechanisms of bacteria-nanoparticle interaction by investigating how TiO₂ nanoparticles impact a model organism, the metal-reducing bacterium Shewanella oneidensis MR-1. In addition to examining the effect of TiO₂ exposure, the effect of synergistic simulated solar irradiation containing UV was explored in this study, as TiO₂ nanoparticles are known photocatalysts. The data reveal that TiO₂ nanoparticles cause an inhibition of S. oneidensis growth at high dosage without compromising cell viability, yet co-exposure of nanoparticles and illumination does not increase the adverse effects on bacterial growth relative to TiO₂ alone. Measurements of intracellular reactive oxygen species and riboflavin secretion, on the same nanoparticle-exposed bacteria, reveal that TiO₂ nanoparticles have no effect on these cell functions, but application of UV-containing illumination with TiO₂ nanoparticles has an impact on the level of riboflavin outside bacterial cells. Finally, gene expression studies were employed to explore how cells respond to TiO₂ nanoparticles and illumination, and these results were correlated with cell growth and cell function assessment. Together these data suggest a minimal impact of TiO₂ NPs and simulated solar irradiation containing UV on S. oneidensis MR-1, and the minimal impact could be accounted for by the nutrient-rich medium used in this work. These measurements demonstrate a comprehensive scheme combining various analytical tools to enable a mechanistic understanding of nanoparticle-cell interactions and to evaluate the potential adverse effects of nanoparticles beyond viability/growth considerations.

Impact of TiO2 nanoparticles on growth, biofilm formation, and flavin secretion in Shewanella oneidensis

Understanding of nanoparticle impacts on critical bacteria functions allows us to gain a mechanistic understanding of toxicity and guides us toward design rules for creating safe nanomaterials. Herein, biofilm formation, a general bacteria function, and riboflavin secretion, a species-specific function, were monitored in Shewanella oneidensis, a metal reducing bacterium, following exposure to a variety of TiO2 nanoparticle types (synthesized, Aeroxide P25, and T-Eco). Transmission electron microscopy (TEM) images show that dosed nanoparticles are in close proximity to the bacteria, but they are not internalized. Using quartz crystal microbalance (QCM), it was revealed that S. oneidensis biofilm formation is slowed in the presence of nanoparticles. Though S. oneidensis grows more slowly in the presence of TiO2 nanoparticles, riboflavin secretion, a function related to the S. oneidensis metal reducing capacity, was increased significantly in a nanoparticle dose-dependent manner. Both changes in biofilm formation and riboflavin secretion are supported by changes in gene expression in nanoparticle-exposed S. oneidensis. This broad study of bacterial nanotoxicity, including use of sensitive analytical tools for functional assessments of biofilm formation, riboflavin secretion, and gene expression, has implications for total ecosystem health as the use of engineered nanoparticles grows.

Toxicity of engineered nanoparticles in the environment

While nanoparticles occur naturally in the environment and have been intentionally used for centuries, the production and use of engineered nanoparticles has seen a recent spike, which makes environmental release almost certain. Therefore, recent efforts to characterize the toxicity of engineered nanoparticles have focused on the environmental implications, including exploration of toxicity to organisms from wide-ranging parts of the ecosystem food webs. Herein, we summarize the current understanding of toxicity of engineered nanoparticles to representatives of various trophic levels, including bacteria, plants, and multicellular aquatic/terrestrial organisms, to highlight important challenges within the field of econanotoxicity, challenges that analytical chemists are expertly poised to address.